Selecting a Level-2 Charger

[DucRider]

I believe Tesla's come w/adpaters so that I should be able to use the ClipperCreek {charger} EVSE with it if I get one. If that won't work, I'd either buy/install a Tesla charger and sell the ClipperCreek which will be easy to remove since it's a plug-in model.

Yes, current Teslas have the J1772 adapter included.
You might consider pulling beefier wire to handle a higher power EVSE to "future proof" your circuit. Current Tesla offerings support 48A L2 charging (60A circuit) and optionally 72A (90A circuit).
Since we don't have any real details on the Model 3, charging capabilities are an unknown. We do know it will be Supercharger compatible, so will very likely use the same connector as the S/X. The on board charger specs are a complete unknown. It may or may not support the same 48A as current models (it could be reduced on the base $35K model to save costs - or garner upgrade $$). The J1772 adapter may be an extra cost option - currently $95.

 

[devbolt]

NEC code says that a NEMA 14-50 outlet is supposed to have a 50A breaker.

That's not actually true. For a branch circuit that feeds just one receptacle, the only requirement is that the receptacle size be no smaller than the breaker size (NEC 210.21(B)(1)).

So a 50 amp receptacle on a 40 amp breaker is just fine. Since there are no NEMA 40 amp receptacles, it's the only way to install a receptacle on a 40 amp circuit.

Cheers, Wayne

I fully admit to not being an electrician, but the paranoid homeowner in me says that if you have a receptacle that is rated for 50A, there is the possibility that a device that is rated for 50A could be plugged into it, and should be protected by a 50A breaker with the appropriate wiring. Downsizing the wiring and breaker seems like it could crate a potential fire hazard if you have a 40A device plugged in that is under continuous use. This would cause the wires to heat up, but the breaker would never trip since it's right at the tripping point.

 

[devbolt]

I bought the juicebox Pro 40. 40A is more than the bolt will draw (30A), but for the $100 more than the regular Juicebox 40 you get wifi connectivity. I want it so I can have a log of my home charging so I can use it as a write off since the bolt is my main vehicle for business. This way I can accurately log how much electricity goes to the home VS the bolt. But also has other good features which let's you control/monitor the charge from the app.
Only bought a 40A dual pole breaker for my panel as the 50A was pricy. Ran 8AWG 3 conductor armoured cable to the NEMA 14-50 plug. 7M of cable, breaker, plug, box, connectors, etc set me back just over $100. So pretty cheap, then hooked up to the panel. Fairly easy job.

NEC code says that a NEMA 14-50 outlet is supposed to have a 50A breaker. Don't be a cheapskate when it comes to the electrical system of your house. Putting the wrong size breaker on that circuit could result in a fire if something goes wrong with the JuiceBox or the Bolt. Be smart and put in the right size breaker for the outlet and for the JuiceBox to use. And technically you might need to run 6AWG wiring for the plug. It's that whole continuous use de-rating thing that's going on...

No harm can result by using a smaller breaker than the rest of the circuit (wires and receptacle) can safely handle. All that happens is that if a dryer, For example, would be plugged into the outlet the breaker would trip.

Yes, this installation is inconsistent with normal practice but it's not unsafe. Unsafe would be to use too large a breaker

You are probably correct, but if I see a 14-50 receptacle, I assume it's capable of actually delivering 50A of service and I don't have to worry about the breaker trippin if I plug something in that is designed to pull 50A. I also assume that the wiring is sized for that potential 50A load.

My EVSE is hardwired, so I haven't had to deal with any of this nonsense.

 

[wwhitney]

Downsizing the wiring and breaker seems like it could crate a potential fire hazard if you have a 40A device plugged in that is under continuous use. This would cause the wires to heat up, but the breaker would never trip since it's right at the tripping point.

Actually, the strong likelihood that a 40A breaker would thermally trip at 40A continuous load is the only reason that continuous loads require a circuit sized at 125% of the continuous load. The 40A rated wiring is good for 40A continuous. In your scenario there would be no fire hazard.

In general it is unwarranted to assume that a NEMA 50 amp receptacle will be on a 50 amp circuit; it could be either 40 amps or 50 amps.

Cheers, Wayne

 

[EldRick]

So you put a 30a outlet on the circuit to protect against future accidents...
The only difference between 30a and 50a outlets is the fourth neutral "pin", which is shaped so that a 50a plug cannot be inserted in a 30a outlet. Interestingly, most EVSEs don't have a Neutral pin on their plug, so they can be used with 30a or 50a outlets.

 

[Anonymous]

I also carry a couple of 240v adapters from http://www.evseadapters.com in case I come across a different outlet than the one my AV TurboCord uses.

 

[devbolt]

Downsizing the wiring and breaker seems like it could crate a potential fire hazard if you have a 40A device plugged in that is under continuous use. This would cause the wires to heat up, but the breaker would never trip since it's right at the tripping point.

Actually, the strong likelihood that a 40A breaker would thermally trip at 40A continuous load is the only reason that continuous loads require a circuit sized at 125% of the continuous load. The 40A rated wiring is good for 40A continuous. In your scenario there would be no fire hazard.

In general it is unwarranted to assume that a NEMA 50 amp receptacle will be on a 50 amp circuit; it could be either 40 amps or 50 amps.

Cheers, Wayne

My research says otherwise. If you have a 40A continuous load, it should be on a 50A circuit with wiring that is rated for 50A.

https://jadelearning.com/jadecc/courses/UNIVERSAL/NEC05.php?imDif=2508

I stand by my statement that if you are installing a 40A (9.6 kW) EVSE and using a NEMA 14-50 receptacle, it should be fed by a 50A breaker and 6AWG wiring on the off chance that someone plugs in a Tesla even though only the Bolt will probably ever be charged.

 

[Anonymous]

I agree: a 14-50 tells the world that it is wired to handle 50 amps!

 

[EldRick]

"NEMA 14-50 receptacle, it should be fed by a 50A breaker and 6AWG wiring"
Actually, electrical code only requires 8ga. for a relatively short 25 ft. 50a circuit.
6ga. or even 4ga. can be required for longer runs, mainly because the voltage drop would be less.

 

[wwhitney]

So you put a 30a outlet on the circuit to protect against future accidents...

A 30A receptacle needs to be protected at 30A or less, so that would limit you to a 30A circuit.

Cheers, Wayne

 

[wwhitney]

Actually, electrical code only requires 8ga. for a relatively short 25 ft. 50a circuit.

The minimum wire size required for a 50A circuit depends on the insulation temperature of the conductors. If you use NM cable, you are restricted to the 60C ampacity values, which means #8 copper has an ampacity of 40A, and you need to use a minimum of #6 copper (55A ampacity). Almost all other wiring methods can take advantage of the 75C ampacity, where #8 copper has an ampacity of 50A and would be adequate for a 50A circuit.

Cheers, Wayne

 

[wwhitney]

If you have a 40A continuous load, it should be on a 50A circuit with wiring that is rated for 50A.

I agree, I never said otherwise. The reason for that rule is not that 40A continuous on a 40A conductor would damage the conductor and be a fire hazard; it's that 40A continuous would likely trip a standard 40a breaker. To avoid that, you need to upsize the breaker to 50A; at which point the wire needs to be upsized to 50A as well, so that the wire is properly protected by the breaker.

So if you plug a 40A EVSE into a 40A circuit (and charge a car that can draw 40A), there won't be a fire hazard. The breaker however, may not hold, which would be a nuisance. Hopefully when the breaker trips, the user will notice that the circuit is only 40A, and realize that a maximum 32A EVSE should be used on that circuit.

I stand by my statement that if you are installing a 40A (9.6 kW) EVSE and using a NEMA 14-50 receptacle, it should be fed by a 50A breaker and 6AWG wiring.

Absolutely. But if you are installing a 30A (7.2 kW) or 32A EVSE, it is code compliant and reasonable to use 40A wiring, a 40A breaker, and a 14-50 or 6-50 receptacle.

Cheers, Wayne

 

[wwhitney]

I agree: a 14-50 tells the world that it is wired to handle 50 amps!

That's an unwarranted assumption; there are plenty of 14-50 or 6-50 receptacles in the wild that are (NEC compliantly) wired on 40A circuits. I believe that some welders may come with a 6-50 plug but require only a 20A or 30A circuit, so you might also run into 6-50 receptacles that are 20A or 30A circuits.

Cheers, Wayne

 

[Anonymous]

How am I supposed to know that they are only wired for 40 amps when I plug my 50 amp appliance into it?

 

[wwhitney]

How am I supposed to know that they are only wired for 40 amps when I plug my 50 amp appliance into it?

Well, if you are lucky the installer labeled the receptacle. NEMA 14-50 receptacles are rare enough that they are typically dedicated to a specific piece of equipment, so if you find a receptacle with the equipment plugged in, you can check the nameplate of that equipment. Otherwise, you need to find the breaker that controls the receptacle, and see if it is a 40 amp or a 50 amp breaker.

Cheers, Wayne

 

[Anonymous]

How am I supposed to know that they are only wired for 40 amps when I plug my 50 amp appliance into it?

Well, if you are lucky the installer labeled the receptacle...
Cheers, Wayne

Really?!? :lol:

I was visiting a home in Northern San Diego County recently and in the garage there is a 14-50 outlet which works with my adapter and the AV TurboCord to charge my Bolt EV. Of course I am not expecting to draw 50 amps out of it, but maybe someone will come by with a welding unit someday...

 

[michael]

Let's do a mental experiment.

6-50 outlet, 8 ga wires, 15 Ampere breaker.

Is there any fire hazard?

6-50 outlet, 10 ga wires, 15 Ampere breaker.

Is there any fire hazard?


I claim that in both cases there is no hazard other than unexpected tripping of the breaker. Yes, it's true that a 6-50 outlet advertises 50 A capability, but the breaker protects the circuit. It's not good practice to mix ratings, but this combination is not a hazard, it's at worst a potential inconvenience.

 

[SparkE]

How am I supposed to know that they are only wired for 40 amps when I plug my 50 amp appliance into it?

The breaker trips, silly !!

 

[Anonymous]

How am I supposed to know that they are only wired for 40 amps when I plug my 50 amp appliance into it?

The breaker trips, silly !!

Want to consider something something silly:
Glad you have confidence in circuit breakers made in China!

 

[sgt1372]

Regarding the foregoing discussion, I'm going to tell my electrician to install a 50A circuit w/appropriate wiring to the NEMA 14-50 outlet. I assume the circuit will be marked w/50A circuit breakers.